A sonar (an acronym for Sound Navigation and Ranging) is a sensing system which measures features of an environment by the way in which that environment transmits, reflects and/or absorbs acoustic waves. It is generally used to detect objects or to determine their direction/bearing and distance/range. The earliest and simplest sonar imaging measured sound pulse reflections off the ocean floor. By determining the time between the transmission of the pulse and receipt of the reflection of the pulse, dividing by a factor of two, and multiplying by the speed of sound in water, depth could be determined.
Sonar units have many applications for individual, commercial, as well as government use. For example, individuals may use a sonar system to inspect docks and boat hulls, to recover lost objects, to treasure hunt, or to perform geographic and contour mapping of local areas. Commercial users may use sonar units to inspect ship hulls, to inspect oil wells, to assess underwater damage, and to assess fisheries, for example, by locating and mapping fish. Similarly, the government uses sonar units to perform underwater surveillance for security, reconnaissance, ordinance classification and hydrographic surveys; to recover lost objects; to train divers; to train marine mammals; to rescue people; to assess damage; and to inspect ship hulls.
Traditional sonar systems of similar application fall into three categories: single beam mechanical scan, single beam hand held, and multiple beam hand held. Each of these types of systems have limitations which can limit their usefulness. Existing mechanically scanned single beam sonar units require a stable platform and stepper motors for operation, which preclude use by a diver. Hand held single beam sonar units, on the other hand, only provide range information to the diver who is therefore required to remember the location of all targets. Multiple beam hand held sonar units continuously display range and bearing for targets over a limited sector, but require an amount of circuitry proportional to the sector coverage, thereby increasing the size of the sonar. Thus, the size and power requirements of a multiple beam hand held sonar significantly limit sector extent, resolution, and maneuverability.